Continuous subcutaneous infusion of medications is a prevalent method of drug delivery. Typically, an individual uses a small programmable pump to deliver medication through a flexible plastic tube to an infusion set. The infusion set delivers medication to an individual's subcutaneous tissue through the use of either a rigid needle that is left in the tissue or through a flexible cannula that remains in the tissue after being inserted via a removable needle. The most common infused fluid is insulin. An estimate of over 500,000 individuals worldwide use subcutaneous infusion of insulin for the treatment of diabetes mellitus. However, other infused fluids include HIV drugs, drugs to treat pulmonary hypertension, iron chelation drugs, pain medications, and anti-cancer treatments.
An insulin delivery system generally includes a pump, tubing and infusion set attached to a cannula or needle. The tubing is connected to the pump at one end and connected to the cannula or needle at the other end to deliver the insulin into the body. During the initial set up of the system, the user executes a priming sequence to fill the tubing and cannula or needle with insulin prior to insertion of the cannula or needle into the body.
Existing methods of detecting whether the tubing and cannula or needle is primed with insulin require the user to watch for droplets of insulin forming on the tip of the needle. This method of detection can be challenging for those who have poor vision, especially the elderly and diabetics with impaired vision. In addition, infusion systems can include a needle guard to cover the needle and prevent accidental poking of oneself. Such systems require removal of the needle guard to allow the user to view the insulin droplet form at the tip of the needle during the priming sequence of the pump. Current infusion systems do not provide a noticeably clear method to observe completion of priming without straining the eyesight and/or compromising the safety of the user.